hoover



Feb. 7, 1956 M. v. HOOVER 2,734,144

ELECTRODE POSITIONING MECHANISM Filed April 9, 1952 F 5 j; VNVEN R M MERLE .Hu ER ATTORNEY Unitfid States Paten ELECTRODE POSITIONING MECHANESM Merle V. Hoover, Mountville, Pa., assignor to Radio Corporation of America, a corporation of Delaware Application April 9, 1952, Serial No. 281,298

4 Claims. (Cl. 313--273) This invention relates to electrodes and supporting structures particularly useful in electron discharge devices. It is an improvement upon the invention claimed in co-pending application of William H. Parker, Serial No. 95,432 filed May 26, 1949, now U. S. Patent No. 2,626,370, and is herein described as embodied in a discharge tube of the super power variety shown in the patent to Garner et al. 2,544,664.

The Parker support for rod-like cathodes, grids, furnace heating elements, etc., comprises a stationary U- shape member supported at its base, normal to the rod, and a T-shape electrode terminal which fits between the open ends of the U, with the crossarm of the T spanning the space between the arms of the U. The lower edge of the cross arms of the T is wedge-shape and seats in a complementary V-shape groove in each arm of the U. A spring support at one end of the electrode facilitates the mounting operation and biases the knife-edge of the wedge into contact with the bottom of the V-groove regardless of thermal expansion and contraction of the electrode.

Parkers self-biasing, quickly detachable electrodesupport has proven entirely satisfactory in most installations. However, short circuits have been encountered in pulse operated power tubes wherein the cathode and grid rods were mounted in this manner. it has been observed that pulse operation may set up a harmonious recurrence of stress in the rods and their supports, which may lead to the breakdown. An analysis of the causes of the stress indicates that the faulty operation is due to one or more of the following causes:

(1) The knife-edge electrode-terminal elements are constituted of tungsten or other hard refractory metal and are formed in a die. The hard metal subjects the surfaces of the die to wear and, as a consequence, there may be a substantial degree of non-uniformity in the first and last of a series of knife-edges made by the same die. It is thus impossible, as a practical matter, to avoid play within the grooves in which the knife-edges are seated. The degree of play may be augmented during operation either (a) by the cutting action of the knifeedge terminals upon the copper, or other relatively soft metal in which the terminals are seated, or (b) by fracturing of the hard yet brittle metal of which the knifeedges are formed. (2) The knife-edged elements, when subjected to the pulsed magnetic and electric forces at work in the tube, operate as miniature levers whose fulcrums are the bottoms of the V-grooves. The resulting mechanical vibrations in some cases may become of destructive amplitude because of excessive play in the grooves.

Accordingly, the principal object of the present invention is to provide an improved electrode support and one which shall possess all of the advantages and none of the above-mentioned disadvantages of electrode supports of the Parker variety.

Stated generally, the foregoing and related objects are achieved in accordance with the invention, by the provision (i) of a stationary supporting element, which may be similar in all respects to the grooved U-shape element of the Parker support, and (ii) a preferably T-shape electrode-terminal element wherein the underside of the crossarm of the T is rounded, instead of sharpened, to provide two balanced parallel lines-of-contact with the sloping sides of the groove in the stationary support. Spring biasing means facilitates the assembly operation and permits expansion and contraction of the electrode and its supports and, further, operates automatically to center and to maintain the rounded surface of the T in contact with the slanting surfaces of the groove irrespective of minor irregularities in said surfaces.

The invention is described in greater detail in connection with the accompanying single sheet of drawings wherein:

Fig. 1 is a partly broken-away elevational view of an electron discharge tube of the super-power? variety shown in Garner et a1. 2,544,664 and incorporating cathode and grid supports constructed in accordance with the present invention;

Fig. 2 is a greatly enlarged view in perspective of one of the electrode supporting structures used in the tube of Fig. l;

Fig. 3 is a view partly in section of the assembly taken on the line 3-3 of Fig. 4; and

Fig. 4 is a fragmentary side elevation of the electrode supporting-assembly shown in Figs. 2 and 3.

Referring to Fig. l, electron discharge device 24 is a super power? tube capable of an output of the order of say, 500,000 watts. Electron discharge device 24 is an internally water-cooled triode having a cathode and a grid, each of which comprises a circular array of axially extended discreet elements or bar-like sections indicated specifically at 25 and 26, surrounded by a cylindrical anode 27 and all are housed in a demountable evacuated envelope as shown.

Each of the cathode elements or sections 25 is supported adjacent to its upper ends by a laminated flexible support means indicated generally at 28 and supported from central conducting tubular support member 29 which is connected to a copper diaphragm 38 by means of which the upper end of the element 25 is connected electrically to terminal ring 30.

The other or lower end of each cathode element or section 25 is inflexibly mounted in ring 31 which is brazed to the outer cathode conducting support 32 at the lower end of a beam former array. Conducting support member 32 is coaxial and concentric with conducting support 29 and has a lower portion of increased diameter which, below terminal ring 33, forms part of the interior envelope of the tube. The upper portion of conducting support 32 which is in the active region of the device 24 has a plurality of grooves machined therein, one for each of the cathode sections of which there are forty-eight in the tube illustrated. The grooves are separated by lands 34 which function as the beam former array and focus the electron stream emitted from each cathode section.

It is apparent, therefore, that each cathode element is flexibly mounted at one end to one conducting support member and inflexibly mounted at the other end to the other conducting support member. Further, it should be noted that the conducting supports 29, 32 are rigidly connected by a mechanically strong insulating and her metic seal 39.

Insulated from and supported on central conductor 29 is a hat-shaped grid support member 35 having an annular peripheral flange at its low extremity, with slots and circular centering or locating V notches formed therein. There is one slot for each grid element 26. The grid elements are equal in number to the cathode elements 25. Grid elements 26 each hook into grid support which in turn is supported from a grid terminal ring 37. Support members 28 and 36 are described and claimed in the co-pending application of Willis E. Harbaugh, filed May 26, 1949, Serial No. 95,442, now U. S. Patent 2,570,121.

The cathode, grid and beam former arrays form closely positioned critically spaced units with the cylindrical anode. in the tube illustrated, the cathode and grid elements are tungsten bars approximately eight inches in length and are extremely ductile at elevate temperatures. It is obvious that such a construction would be subject to objectionable deformities during processing and operation which would render it inoperative were the cathode and grid elements not mounted in such manner that they may freely expand and contract without undergoing deformation. Supports 2 and 32 are of copper, while the electrode elements 25, 26 are tungsten bars or rods. Also, magnetic effects on self-heated cathode 25 may introduce undesirable bending moments if there is any binding between the mounting head and its support.

To insure firm contact of each of the electrodes or electrode elements with its supports by way of the halfround bearing surfaces, each electrode is maintained in axial tension. Two arrangements for axially tensioning each of the elements independently are utilized in electron discharge device 24. In the case of cathode elements 25, a coil spring 4t) in a cylindrical tube is provided for each segment of flexible support 28 which acts against an insulating link 41, and which in turn engages rocker arms 42. Rocker arm 42 is free at one end, to pivot in a groove in the lower arm of L-shaped ring 43, while its other end is bifurcated and is engaged in another V groove on the under side of mounting block 44. The coil springs 40, in their cylinders, are arranged in circular array in an annular channel formed by conducting support 32 and seal 39. Grid support members 36 are each resilient and include a plurality of steel laminations which serve to maintain each grid element 26 in axial tension without any additional tensioning means. Cathode and grid elements 25 and 26 respectively, each have a mounting head 11 with half-round bearing surface 12 and fillet, or residual radii, 16 formed at each end thereon. As most clearly seen in Fig. 1, the upper cathode mounting heads are each individually mounted in separate mounting blocks 44 at the end of each segment of flexible support 28; the lower cathode mounting heads being clipped into slotted annular block 31. The upper grid mounting heads are each clipped into an annular peripheral slotted block on support member 35 While the lower grid mounting heads are each clipped into mounting blocks 45 on separate resilient supports 36 which are arranged in radial array.

Referring to Figs. 2 and 3, in accordance with my invention, an electrode ltl has a mounting head 11 provided with a curved surface, here illustrated as a half-round surface 12. The curved surface seats in a V groove 13 that is formed in a mounting block or support 14 and at right angles to a slot 15 also formed in the support 14. The half-round surface 12 contacts the mounting block or support 14 along two lines on the surface of the V-groove 13, the lines of contact being at right angles to the longitudinal axis of the electrode 10. A V-groove angle of 90 has been found to be satisfactory for use with mounting heads having a half-round bearing surface, although other appropriate combinations of curved surfaces and V angles could be used.

The mounting heads of this invention are prepared in accordance with the method disclosed by Parker in his co-pending application, Serial No. 95,432 filed May 26, 1949, now U. S. Patent No. 2,626,370, previously mentioned, except that the contour of the heading dies is changed so that a half-round bearing surface is formed on the electrode rod instead of the V-head or knifeedge which Parker uses.

When electrode mounting heads made according to this invention have been used in demountable tubes of the type described in U. S. Patent 2,544,664 to Garner et a1., quivering of the electrodes has apparently disappeared.

A further advantage of using half-round bearing surfaces is the improved cooling of the electrode resulting from thermal conduction through the greater area of the double lines of contact instead of the single line of contact made by the knife-edge electrode mounting heads.

Although the half-round bearing surface was first used in connection with mounting heads for grid electrodes, it is also applicable to filamentary cathodes or other electrodes. A portion 17 of reduced cross-section adjacent each end of the electrode prevents excessive heat loss, by conduction, from the end emitting portions of the electrode. It should also be noted that although the present invention is particularly useful in electron discharge devices, it may also be advantageously used in electric heating furnaces or other devices.

Mounting blocks 44 and 45 are similar to block 14 and are each provided with V grooves and slots. Annular block 31 as well as the annular slotted block on support member 35 are each provided with an annular V groove, not shown. Mounting heads 11, with half-round bearing surface 12, are particularly suited for engaging the surfaces of the annular V groove.

Electron discharge device electrode structures made in accordance with the present invention may be processed, as in the case of high temperature bakeouts, and operated without undergoing deformation. Such electrode structures have been found to be free of kinks or bowing due to bending moments in the mounting heads even after long periods of operation, and have not exhibited tendencies to quiver under normal operation of the tube, and neither the half-round bearing surfaces or the V-grooves have shown excessive Wear.

It is apparent that there has been provided a highly useful device which permits accurate close spacings of electrodes free from undesirable deforming forces and tendencies to quiver during operation of the tube. Furthermore, by providing pressure contact at predetermined local points in accordance with the present invention intermittent contact between the electrode and its supports is effectively eliminated. The foregoing are particularly advantageous in high power or high frequency devices.

What is claimed is:

1. An electron discharge device comprising at least two co-acting electrodes, support means for each of said electrodes, at least one of said electrodes being elongated and having a mounting head adjacent to each of its ends, each of said mounting heads having a curved bearing surface which intersects the longitudinal axis of said elongated electrode, the support means associated with said elongated electrode including means axially tensioning said elongated electrode and means having spaced V grooves formed therein adapted to receive said curved bearing surfaces, each of said curved bearing surfaces being quick detachably seated in contact with portions of one of said V grooves, and said portions of each of said grooves being removed from the apex of each of said grooves.

2. An elongated structure comprising an electrode having spaced apart mounting heads formed thereon, each of said mounting heads having a curved bearing surface formed thereon, means supporting and axially tensioning said electrode and having spaced apart V grooves formed therein, and said electrode being in quick detachable engagement with said means with said curved bearing surfaces seated in the sides of said V grooves at portions thereof removed from the apex of said grooves.

3. An electrode structure, comprising an elongated electrode having mounting heads formed at each end thereof, each of said mounting heads having curved bearing surfaces extending in a plane which intersects the longitudinal axis of said electrode, means supporting and axially tensioning said electrode, said means having spaced apart slotted V grooves formed therein, said electrode extending through said slots with the curved bearing surface on one of said heads in the sides of one of said V grooves remote from the apex thereof and the curved bearing surfaces on the other of said heads in the sides of the other of said V grooves remote from the apex thereof, and a portion of said electrode having a reduced cross section merging with said elongated electrode between said mounting heads, said portion extending through the space between said V grooves when said electrode is positioned in said supporting means.

4. An electron discharge device comprising at least two co-acting electrodes, support means for each of said electrodes, at least one of said electrodes being elongated curved bearing surfaces, each of said curved bearing surfaces being quick detachably seated in contact with portions of one of said converging grooves, and said portions of each of said grooves being removed from the apex of said grooves.

References Cited in the file of this patent UNITED STATES PATENTS 1,839,323 Loewe Jan. 5, 1932 2,266,080 Rockwood Dec. 16, 1941 2,467,390 Kelley Apr. 19, 1949 2,544,664 Garner et al Mar. 13, 1951 2,546,184 Garner Mar. 27, 1951 2,570,121 Harbaugh Oct. 2, 1951 2,626,370 Parker Ian. 20, 1953 

